Stop Saying a Hamstring Stretch Is "Just Stretching the Nerve"
I heard a therapist say this in the clinic the other day.
I had to do a double take.
Were they joking?
Did I hear them wrong?
Or were they just trying to piss me off?
After calming down, I realized something slightly embarrassing.
About ten years ago...
I probably said the exact same thing.
Thankfully, while I may not have become any more mature, my treatment ideas certainly have.
Here’s some thoughts on the above statement:
One of the most confidently repeated statements in rehab is:
"You're not actually stretching your hamstrings. You're just stretching the nerve."
No.
Just stop.
The idea usually comes from the observation that changing ankle position during a hamstring stretch changes how intense the stretch feels. Dorsiflex the ankle and the stretch gets stronger. Point the toes and it gets easier.
What's fascinating is that changing ankle position appears to alter the perception of the stretch far more than it changes the actual length of the hamstring. That's exactly what we'd expect if multiple tissues—including neural tissue—contribute to the sensation. It isn't evidence that the hamstrings have somehow disappeared.
Somehow this turned into:
"See? It's all neural tension. You're not stretching muscle at all."
That's a massive leap.
Anatomy Doesn't Suddenly Disappear
The hamstrings are three large muscles crossing both the hip and knee.
When you flex the hip and extend the knee, the hamstrings get longer.
That's not controversial.
That's not a theory.
That's basic anatomy.
At the same time, the sciatic nerve and its branches are also experiencing increased mechanical loading.
Both things can be true simultaneously.
Yet rehab has this bizarre tendency to turn every discussion into an either-or argument.
It's muscle.
Or nerve.
Pick one.
Reality doesn't care about your false dichotomy.
What the Research Actually Shows
Here's where things get interesting.
The neurodynamics crowd is partly right.
Research shows that peripheral nerves are not passive cables. During movements such as a straight-leg raise, neural tissues slide, glide, elongate, and experience mechanical strain.
A systematic review by Thomas and colleagues (2021) demonstrated that peripheral nerves respond mechanically to stretching and movement. Neural tissues clearly contribute to flexibility, range of motion, and stretch sensation (Thomas et al., 2021).
Great.
Nobody is arguing otherwise.
The problem is what some clinicians do with that information.
They take:
"The nerve contributes."
And somehow arrive at:
"Therefore the muscle doesn't."
Contributing is not the same thing as being solely responsible. Rehab has a bad habit of confusing the two.
That's not how science works.
The Nerve Doesn't Exist in a Vacuum
When people say you're "just stretching the nerve," they act like the nerve is floating through empty space.
Nerves run through muscles.
Between muscles.
Around fascia.
Adjacent to blood vessels.
Through connective tissue tunnels.
When you move, the entire system experiences load.
The nervous system obeys the same laws of mechanics as every other tissue of the body.
The nerve is influenced by muscle tension.
The muscle is influenced by neural drive.
The connective tissues influence both.
It's one interconnected system.
Hamstrings Are Still Real Tissues
If hamstring stretching only affected nerves, then why do studies repeatedly measure changes in hamstring flexibility, stiffness, and mechanical properties following stretching interventions?
Systematic reviews by Cai et al. and Cayco et al. (2023) and Cayco et al. (2019) found that stretching interventions improve hamstring flexibility and alter mechanical behavior within the muscle-tendon unit.
Apparently the hamstrings didn't get the memo that they're not involved.
Neither did every anatomy textbook written in the last 400 years.
Even more amusing is that we routinely discuss hamstring strain injuries occurring during rapid lengthening of the hamstrings (Danielsson et al., 2020).
If the hamstrings aren't being meaningfully lengthened during hip flexion and knee extension, then somebody needs to explain how hamstring strains happen in the first place.
But I Feel More Stretch When I Dorsiflex My Ankle
Of course you do.
Adding ankle dorsiflexion increases mechanical loading throughout the neural system.
Studies comparing neurodynamic techniques and traditional stretching have demonstrated that altering neural tension can change perceived stretch intensity and range of motion (Satkunskiene et al., 2020).
Nobody disputes that.
The mistake is assuming that because the nerve contributes to the sensation, the muscle contributes nothing.
That's like saying because your quadriceps contribute to a squat, your glutes aren't working.
The conclusion doesn't follow.
Changing one component of the system doesn't eliminate the others.
The Real Answer Is Less Exciting
A hamstring stretch loads:
Hamstring muscle tissue
Hamstring tendons
Sciatic nerve
Neural connective tissue
Fascial structures
Joint capsules
Surrounding vascular tissues
Your body doesn't separate these structures into neat little categories during movement.
Only rehab textbooks do.
The body experiences total tissue tension.
We don't stretch isolated tissues.
We stretch people.
And people are wonderfully inconveniently connected.
And before somebody screams, "But the nervous system limits range of motion!"
Sure.
Sometimes.
So do muscles.
So do tendons.
So do joints.
So does fear.
So does pain.
So does tissue sensitivity.
Human movement is messy.
That's why simplistic explanations sell well and age poorly.
The Bigger Problem
The bigger issue is what happens clinically.
A patient says:
"My hamstrings feel tight."
A therapist immediately responds:
"Actually your hamstrings aren't tight. It's neural tension."
How do they know?
Did they measure hamstring stiffness?
Did they assess neural mechanosensitivity?
Did they quantify tissue strain?
No.
They heard something on a podcast and repeated it.
Rehab has become obsessed with sounding smarter rather than being more accurate.
Twenty years ago everything was the SI joint.
Then everything was weak glutes.
Then everything was a dysfunctional transverse abdominis.
Now everything is neural tension.
Different decade.
Same story.
Every generation of therapists thinks it has finally discovered the tissue everyone else missed.
History suggests we'll all be laughing at this one in another ten years.
Clinical Reality
The literature doesn't support the claim that a hamstring stretch is "just stretching the nerve."
Research supports something far less sexy:
Neural tissues experience strain during stretching.
Hamstring muscles experience strain during stretching.
Connective tissues experience strain during stretching.
All of these structures contribute to the sensation and mechanics of movement.
The evidence supports a multi-tissue model.
Not a single-tissue explanation.
Rehab has an uncanny ability to discover something real...and then immediately pretend it's the only thing that's real.
The next time someone tells you that a hamstring stretch is "just stretching the nerve," ask them one simple question:
If the hamstrings aren't being stretched, what exactly is getting longer when you flex the hip and straighten the knee?
Don't worry. The anatomy will still be there when the argument is over.
-the Pissed-Off PT- unshare, dislike, don’t comment-
References
Thomas E, Bianco A, Paoli A, Palma A. Peripheral Nerve Responses to Muscle Stretching: A Systematic Review. Sports Medicine. 2021.
Satkunskiene D, et al. Immediate effects of neurodynamic nerve gliding versus static stretching on hamstring neuromechanical properties. Journal of Sports Science and Medicine. 2020.
Cai C, Au IPH, An W, Cheung RTH. Dynamic and static stretching on hamstring flexibility and stiffness: A systematic review and meta-analysis. Heliyon. 2023.
Cayco CS, Labro AV, Gorgon EJR. Hold-Relax and Contract-Relax Stretching for Hamstring Flexibility: A Systematic Review with Meta-Analysis. Physical Therapy in Sport. 2019.
David Butler. The Sensitive Nervous System. NOI Group.
Michael Shacklock. Clinical Neurodynamics: A New System of Neuromusculoskeletal Treatment.
Danielsson A, Horvath A, Senorski EH, et al. The mechanism of hamstring injuries: a systematic review. BMC Musculoskeletal Disorders. 2020.